Largest Number

• Time : $O(nlogn)$
• Space : $O(n)$

string Solution::largestNumber(const vector<int> &A) {
    vector<string> AA;
    for(auto& a : A) AA.push_back(to_string(a));
    sort(rbegin(AA), rend(AA), [](auto a, auto b) {
        return a + b < b + a;
    });
    string res = "";
    for(auto& s : AA) res+=s;
    reverse(begin(res), end(res));
    while(res.size() > 1 and res.back() == '0') res.pop_back();
    reverse(begin(res), end(res));
    return res;
}